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Biology A-Level > Chapter 14: Responses to stimuli > Flashcards

Chapter 14: Responses to stimuli Flashcards

1
Q

stimuli

A

a change in the internal or external environment that leads to a response

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2
Q

taxes

A

a simple response seen in animals that involves movement away or towards a stimulus

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3
Q

kinesis

A

a simple response to a non-directional stimulus (humidity) in which the organism changes the speed at which it moves and the rate at which it changes direction

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4
Q

tropism

A

a plant growth response to a directional stimulus

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5
Q

receptor

A

detect stimuli

specific to one type of stimuli

e.g. light, pressure, glucose conc.

many different types

can be cells or proteins found on cell-membranes

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6
Q

effector

A

carries out a response

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7
Q

coordinator

A

formulates an appropriate response to a stimuli

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8
Q

negative taxes

A

a form of taxes that involves moving away from an unfavourable stimulus

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9
Q

positive taxes

A

a form of taxes that involves moving towards a favourable stimulus

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10
Q

positive tropism

A

…

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11
Q

negative tropism

A

…

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12
Q

phototropism

A

plant growth in response to light

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13
Q

gravitropism

A

growth in response to gravity

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14
Q

Why is it important that animals respond to stimuli?

A

The ability to respond to stimul

  • increases chances of survival
  • avoiding harmful environments
  • maintain optimal internal enviornments for metabolism
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15
Q

reflexes

A

automatic, rapid responses to stimuli

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16
Q

Why are reflexes important?

A

automatic - don’t have to think/decide - rapid

reduce amount of harm/protect the body

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17
Q

relfex arc

A

the pathway of neurones linking receptors to effectors in a relfex

18
Q

Briefly describe a simple reflex arc

A

stimulus

heat

receptor

thermoreceptors in skin detect heat

sensory neurone

send impulse from receptor to relay neurone

relay neurone

sends impulse from sensory to motor neurone

motor neurone

sends impulse to effector

effector

bicep muscle contracts to pull arm away

19
Q

When can a reflex be overriden?

A

If there is a relay neurone in the reflex arc the reflex can be overriden

20
Q

Characteristics of nervous communication.

A

localised

neurotransmiter are released directly onto target cells

short-lived

neurotransmitters are removed

rapid

electrical impulses travel fast

21
Q

Why is it important for plants to be able to respond to stimuli?

A

increases their chances of survival

  • allows them to grow towards light
  • maximum absorption of light for photosynthesis
  • roots can grow in the right direction
  • climbing plants can find things to climb to reach sunlight
22
Q

Are shoots negatively or positively phototropic?

A

Shoots are positively phototropic

They grow towards light.

23
Q

Are roots negatively or positively phototropic?

A

Roots are negatively phototropic

They grow away from light

24
Q

Are shoots negatively or positively gravitropic?

A

Shoot are negatively gravitropic.

They grow upwards

25
Q

Are roots negatively or positively gravitropic?

A

Roots are positively gravitropic

They grow downwards

26
Q

growth factors

A

hormone-like chemicals that speed up or slow down plant growth

produced in the growing parts of a plant (the tips of shoots and leaves)

transported to where they are neeeded

27
Q

auxin

A

type of growth factor

in the shoots auxin stimulates growth in shoots by cell elongation where cell walls become stretched and loose making the cells longer

in the roots auxin inhibits cell elongation and growth

indoleacetic acid (IAA) is an auxin

28
Q

Indoleacetic acid

A

an auxin produced in the shoot tips of flowering plants

moved around the plant to control tropism over short distances via diffusion and active transport and over long distance via the phloem

29
Q

Briefly describe how phototropism works in the shoot tips of a plant.

A
  1. light comes in from one direction
  2. one side of the shoot receives more light than the other
  3. IAA builds up on the shaded side
  4. this uneven distribution menas uneven growth
  5. the higher concentration of IAA causes cell elongation on the shaded side
  6. the shoot bends towards the light
30
Q

Briefly describe how phototropism works in the root tips of a plant.

A
  1. light comes in from one direction
  2. one side of the root receives more light than the other
  3. IAA builds up on the shaded side
  4. this uneven distribution means uneven growth
  5. the higher concentration of IAA inhibits growth
  6. the root bends away from the light
31
Q

Briefly describe how gravitropism works in the shoots and roots of a plant.

A
  1. IAA builds up on the underside/lowerside of shoot and roots
  2. this uneven distribution means uneven growth
  3. the higher conc. of IAA on the underside of shoots causes cell elongation
  4. so that shoots grow upwards
  5. the higher conc. of IAA on the underside of roots inhibits cell growth
  6. so that roots grow downwards
32
Q

How does kinesis keep simple organisms in a favourable environment?

A

kinesis

favourable: move slowly and don’t change direction as often so increases chance of staying in a favourable area

unfavourable: increase speed and turn more often so increases chance of moving into a favourable area -improving chances of survival

e.g. woodlice use kinesis to stay in areas of high humidity - reduces water loss and helps to conceal them

33
Q

Pacinian corpuscle

A

receptors found deep in the skin

hands, soles of the feet, external genetalia, ligaments, etc

detect mechanical stimuli

changes in pressure/vibrations

a single sensory neurone or sensory nerve ending wrapped in layers of cell tissue/connective tissue called lamellae

34
Q

photoreceptors

A

light receptors found in the eye

convert light into an electrical impulse

35
Q

cones

A

a type of photoreceptor found packed in the fovea of the retina that give trichromatic vision

36
Q

rods cells

A

a type of photoreceptor found in the peripheral parts of the retina that give us monochromatic vision

37
Q

Briefly decribe what happens when a Pascinian corpuscle is in its resting state and when it is stimulated.

A

Resting:

  • resting potential
  • the stretch-mediated sodium channels are too narrow to let sodium ions to diffuse in
  • the inside is more negative than the outside

Stimulated:

  • Pressure is applied and the membrane is stretched/deformed
  • causes stretch-mediated sodium channels to widen
  • sodium ions able to diffuse in
  • influx of sodium ions causes depolarisation of the membrane
  • inside becomes more positive than the outside
  • called the generator potential
  • the generator potential could lead to an action potential
38
Q

rod cells

A

low visual acuity

retinal convergeance

  • more numerous than cone cells

sensitive

  • monochromatic vision because different wavelengths cannot be distinguished
    *
39
Q

retinal convergeance

A

lots of rod cells are connected to 1 sensory neurone

this means that it is more likely that the threshold value will be reached to create a generator potential

becase lots of low level depolarisations in the rod cells can accumulate to reach the threshold value

40
Q

What does it mean for rod cells to have low visual acuity?

A
41
Q

What is the pigment found in rod cells?

A

Rhodopsin

42
Q

control of heart rate

A

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Biology A-Level (24 decks)

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